1. Field of the Invention
The present invention relates to the conference function of a telephone exchange system, and more particularly to a method of call conferencing for conference participants to communicate directly with each other.
2. Related Art
Generally, the telephone exchange system performs the basic function to establish communications between any subscriber lines in the same and different exchanges, between any subscriber line and any sub scriber's extension line, and between extension lines in the same private branch exchange. In addition to the basic function, the exchange system provides various convenient functions in the idle and busy states such as last number redial, speed dial, do-not-disturb, hold, and conference functions.
U.S. Pat. No. 4,475,193 entitled Power Line Carrier Multi Telephone Extension System For Full Duplex Conferencing Between Telephones to Brown discloses a power line carrier telephone extension system for transmitting electrical signals between the telephone line and an extension telephone over the AC electric power line available at a telephone subscriber's premises, that includes a main station for processing signals between the subscriber's telephone line and power lines and an extension telephone of the system that plugs into the power line. Means are disclosed that provides for a plurality of such extension telephones all of which can place calls to the telephone line, answer calls from the telephone line and conference together in full duplex communication.
U.S. Pat. No. 4,514,594 entitled Power Line Carrier Telephone Extension System For Full Duplex Conferencing Between Telephones And Having Telephone Call Hold Capability to Brown et al. disclose a power line carrier telephone extension system for transmitting electrical signals between the telephone line and one or more extension telephones over the AC electric power line available at a telephone subscriber's premises, that includes a main station for processing signals between the subscriber's telephone line and power lines and one or more extension telephones of the system that plugs into the power line, all of which can place calls to the telephone line, answer calls from the telephone line and conference together in full duplex communication. Means are disclosed that at the extension telephones for initiating a telephone line hold signal that is transmitted over the power line to the main station where the hold signal is detected and initiates connecting a hold impedance across the telephone line.
U.S. Pat. No. 4,523,307 entitled Power Line Carrier Multi Telephone Extension System For Full Duplex Conferencing And Intercom Between Telephones to Brown et al disclose a power line carrier telephone extension system for transmitting electrical signals between the telephone line and an extension telephone over the AC electric Power line available at a telephone subscriber's premises, that includes a main station for processing signals between the subscriber's telephone line and power lines and two or more extension telephones of the system that plug into the power line. Means are disclosed that provides for two or more of the system telephones to communicate without going on the telephone line (Intercom), even while another system telephone is engaged in an outside telephone call and means are further disclosed to provide for all telephones of the system to conference in Intercom.
U.S. Pat. No. 4,665,545 entitled Communication System Having Multi-Mode Line Selection Buttons to Galensky et al. disclose a communication system that includes station sets having one or more function enable buttons and a plurality of line access buttons. It is disclosed that the function enable buttons include the extension, transfer and send message buttons. Each line select button is disclosed as being associated with a communication line and with the station set associated with that line. Operation of a function enable button is disclosed to initiate the feature associated with that button and also changes the function of a line select button from a line access button to an auto-dial select button for dialing the station associated with the line select button.
U.S. Pat. No. 4,984,263 entitled Break-In Method In A Key System to Eun discloses a break-in method and a circuit in a key system for switching a key system to a conference-call state by use of a conference-call circuit. In the break-in method, it is disclosed that when an attendant perceives a telephone subscriber on the line, the attendant breaks in forcefully upon the subscriber's call currently on the line, changing the present call to a conference call. Thereafter, it is disclosed that if the attendant hangs on the phone, the subscriber having waited for being switched breaks into the conference-call replacing the attendant.
U.S. Pat. No. 5,090,052 entitled Telephone System With Multiple Extension Telephones to Nakajima et al. disclose an improved telephone system in which a plurality of telephone units connected to a common telephone line is directly connected to an outside telephone line, with each telephone unit disclosed as containing complete capability for making outside calls, for making extension calls, and for the automatic exchange control of the use of the common telephone line. It is disclosed the telephone system provides functions, including making multiple simultaneous calls on a single telephone line without requiring separate exchange equipment, additional extension or signal lines. Also, it is disclosed telephone units in this system can be connected to more than one outside telephone line to expand the system capacity.
U.S. Pat. No. 5,319,702 entitled Method And Apparatus For Detecting And Responding To Hook Flash Events Occurring On A Remote Telephone to Kitchin et al. disclose methods and apparatus for use in conjunction with a telephone or with equipment in telecommunication with a remote telephone. It is disclosed apparatus provides an indication as to whether a remote party using the remote telephone has performed a specific act causing the generation of a hook flash-type signal which is detected by the apparatus. It is disclosed the apparatus includes software for cooperating with the energy detector to detect a specific event(s) occurring on the telephone line during a predetermined maximum time window following the detection of a specific pulse, with the detection of the specific event(s) providing an indication as to whether the remote party has performed a specific act such as attempting to initiate a 3-way conference call.
U.S. Pat. No. 5,442,688 entitled Multiple Party Telephone Control System to Katz discloses to interface a primary telephone terminal with a vast number of remote terminals through a telephone network, parties at the remote terminals are individually screened to attain a select group. It is disclosed that bridged together, the select group is preliminarily informed of the status of the interface by a voice generator and, accordingly, the multitude of connections are synchronized for the interface. On cue, the select group is disclosed as being coupled to the primary telephone terminal for unilateral communications. Deviations from the unilateral communication are disclosed as including select bilateral communication for a few of the remote terminals and digital communication from the remote terminals by push button as for polling applications.
U.S. Pat. No. 5,539,812 entitled Method And Apparatus For Detecting An Attempted Three-Way Conference Call On A Remote Telephone to Kitchin et al. disclose methods and apparatus for use in connection with a telecommunication between a local telephone and a remote telephone, which are disclosed as being capable of detecting whether one of the parties to the communication has attempted to initiate a three-way, i.e., conference, call by using a hook-flash signal.
U.S. Pat. No. 5,588,037 entitled Remote Access Telephone Control System, to Fuller et al. disclose a telephone switching and control system connected to a telephone network for providing telephone calling services to an authorized user. It is disclosed the telephone switching and control system includes at least one switch for concurrently servicing a plurality of users, and at least one controller for receiving user authorization information, controlling the at least one switch and, during a call from the user, permitting that call to be extended to one or more network addresses in a series of extensions of that call without requiring the user to go on hook. A method is also disclosed of providing telephone calling services to an authorized user, the method including (a) concurrently providing telephone services to a plurality of users and (b) upon receiving user authorization information during a call from a user, permitting the user to extend that call to one or more network addresses in a series of extensions of that call without requiring the user to go on hook between extensions of that call.
U.S. Pat. No. 5,699,352 entitled Distributed Teleconferencing System to Kriete et al. disclose a distributed teleconferencing bridge system that allows an attendant to control multiple conferences on multiple bridges through a network interface unit. It is disclosed that the attendant can add or delete conferees with a minimum of inconvenience to the conferees while maximizing the use of the bridges by setting up multiple conferences on multiple bridges from a single operating console. Multiple consoles are disclosed as allowing multiple operators to control any number of conferences.
U.S. Pat. No. 5,764,743 entitled Method Of Controlling Operation Of A Multi-Line Telephone Apparatus to Goedken et al. disclose a method of operating a multi-line telephone apparatus including, when a phone line switch is actuated, taking a phone line off-hook when the line is on-hook and bringing the phone line on-hook when the line is off-hook. It is disclosed when the phone line is off-hook and a hold switch is actuated, a hold condition is placed on the phone line when the line is not on hold and removed when the line is on hold. It is disclosed when a phone call is established on a first phone line and a conference switch is actuated, a second phone line is brought off-hook and a conference call connection is established. It is disclosed a common conventional method of making a conference call, which includes actuations of hold switch and phone line switches is retained.
An exchange system exemplary of contemporary practice in the art includes an exchange circuit, a C.O. line interface, an extension interface, and a controller. Besides, it is well known that such exchange system further comprises a dual tone multi-frequency (DTMF) generator, a DTMF receiver, and a ring generator, etc. in addition to such constituent elements. The C.O. line interface interfaces to the subscriber loop, and the extension interface interfaces to the extension subscribers' lines at the user terminals of which general telephone sets or multi-function telephones such as a digital telephone capable of providing various convenient services to subscribers can be connected.
The outer construction of the digital telephone capable of being connected as an extension subscriber to the above exchange system comprises a handset, a liquid crystal display, function keypads, a pushbutton dialing pad, and a volume control. The above function keypad comprises a plurality of keys by which a plurality of variable functions can be set, and the function keypad comprises a plurality of fixed keys such as REDIAL (redialing key), SPEED (speed dialing key), DND (do-not-disturb key), PAGING (paging key), XFER (transfer key), CONN (reconnetion key), HOLD (speak hold key), SPEAKER (speaker mode key). As described above, the above digital telephone set is provided with a variable function keypad and a fixed function keypad so that the subscribers can receive various convenient services to which the conference function according to the present invention is related.
The conference function exemplary of contemporary practice in the art includes the steps of calling another subscriber after holding the line of the current speaking partner during conference, and adding such another partner to the conference group by pressing the conference function key or entering a conference function code when receiving the corresponding subscriber's response. To describe more concretely, the presiding subscriber must hold first the current speaking partner during a two-way conference, and then call another subscriber (on the extension line or the subscriber line), whereby when the called subscriber responds and speaking is established, the presiding subscriber presses the conference function key (CONF key) or enters the prescribed conference code (XFER, #,7) so that the three-way conference between the subscribers can be started.
As described above, in the conference call method exemplary of contemporary practice in the art, a presiding subscriber participating in the current conference must hold first the speaking partner and then call another party to additionally participate, thereupon pressing the conference function key or entering the conference function code to establish such additional speaking participation, which means consequently that the conference call can be established only by a one-sided request for conference. In other words, participants may participate in a conference irrelevant to their wishes, and an intending participant can not participate in a conference if not called by the presiding party.
Besides, a digital telephone set serving as an extension subscriber can be set for a multiline subscriber, wherein the multiline subscriber means a telephone set that can use not only its own primary line but also another subscriber line as a secondary line. That is, a multiline subscriber's phone number is owned jointly by several subscribers, wherein such a multiline telephone set enables phone communication by using its own phone number as well as another subscriber's phone number.
The function keypad of such a multiline telephone set is provided with a plurality of keys (loop keys) corresponding to the respective phone numbers. Therefore, when receiving an incoming signal, the multiline telephone set blinks the lamp of the corresponding multiline loop key, thereby generating a ringing tone to indicate that the line is being called. Even when a multiline subscriber answers the telephone call, the lamp of the above relevant multiline loop key continues to blink, so that another multiline subscriber can know which line is currently busy. Further, even such a multiline subscriber can perform the conference function in the same manner as above described.
The conference function exemplary of contemporary practice in the art has the following drawbacks. First, in order to make a conference call, a complicated procedure such as holding, speaking, and function keying or function code entry must be performed. Second, the conference function can not be performed unless a subscriber invites another subscriber to the conference. Third, when a third party is invited to the conference, one of the current conference participants must be placed on hold and wait for a further response. Fourth, for example, when a person transfers an incoming signal to another person, the person must actuate the hold key and wait for other person's response.